Charging Circuit for a Vehicle-Side Electrical Energy Store

ABSTRACT

Various embodiments of the teachings herein include a charging circuit for a vehicle-side electrical energy store comprising: an alternating current terminal; at least two smoothing capacitors; a configuration device; and a rectifier connecting the alternating current terminal to the configuration device. The configuration device connects the rectifier to the smoothing capacitors, and the configuration device is programmed to connect the smoothing capacitors to one another in a first parallel connection and a second series connection. The alternating current terminal comprises a neutral conductor terminal connected to the configuration device via a diode circuit. The configuration device comprises a first switch connecting the smoothing capacitors to one another in parallel when closed. The configuration device comprises a diode connecting the smoothing capacitors to one another in series when closed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application of InternationalApplication No. PCT/EP2019/074846 filed Sep. 17, 2019, which designatesthe United States of America, and claims priority to DE Application No.10 2018 216 233.6 filed Sep. 24, 2018, the contents of which are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to energy accumulators. Variousembodiments of the teachings herein may include energy accumulatorsand/or vehicles with an electric drive.

BACKGROUND

Vehicles with an electric drive, that is to say vehicles that havepurely electrical drive as well as hybrid vehicles, have an electricalenergy store, in particular in the form of an accumulator. In order tocharge said store with external means they may have an alternatingcurrent connection. This alternating current connection is provided touse energy from an AC grid, such as a public supply grid, for chargingthe vehicle. Vehicles of this sort are also referred to as “plug-invehicles”.

On one hand the energy store must, for technical reasons, be chargedwith DC voltage, so that rectification is required, and on the otherhand adjustments between the operating or rated voltage of the energystore on the one hand and the level of the alternating voltage, or ofthe rectified voltage generated therefrom, may be necessary. It isfurthermore desirable for it to be possible to charge the energy storeof the vehicle equally well with single-phase or with polyphasealternating voltage, in order to be able to realize the shorter chargingtime enabled through the higher interlinking factor of three-phasecurrent.

In addition to these requirements, the costs for semiconductors andother components for corresponding charging circuits that are suitable,both from the point of view of current-carrying capacity and of voltagerating, must be considered. In the light of these costs, the task is toindicate a possible way in which an energy store of a vehicle can becharged using economical components.

SUMMARY

Various embodiments of the teachings herein include a charging circuit(LS) for a vehicle-side electrical energy store (ES), wherein thecharging circuit comprises: an alternating current terminal (WA), atleast two smoothing capacitors (C1, C2), a configuration device (KV) anda rectifier (GR) via which the alternating current terminal (WA) isconnected to the configuration device (KV), wherein the configurationdevice (KV) connects the rectifier (GR) to the smoothing capacitors (C1,C2) and is configured to connect the smoothing capacitors (C1, C2) toone another optionally in a parallel or series configuration, whereinthe alternating current terminal comprises a neutral conductor terminal(N) that is connected to the configuration device (KV) via a diodecircuit (DE), wherein the configuration device (KV) comprises at leastone first switch (S1, S3) that is provided in the configuration device(KV) such that, in the closed state, it connects the smoothingcapacitors (C1, C2) to one another in parallel, wherein theconfiguration device (KV) comprises a diode (DS) that is provided in theconfiguration device (KV) such that, in the closed state, it connectsthe smoothing capacitors (C1, C2) to one another in series.

In some embodiments, the configuration device (KV) comprises two firstswitches (S1, S3) and a diode (DS) that are connected to one another ina series circuit that is connected to different potentials (P+, P−) ofthe rectifier (GR), wherein the first switches (S1, S3) are connected toone another within the series circuit via the diode (DS).

In some embodiments, the diode circuit (DE) is designed as a rectifiercircuit that comprises an alternating current side that is connected tothe neutral conductor terminal (N) and that comprises a direct currentside that is connected to the configuration device (KV).

In some embodiments, the diode circuit (DE) comprises at least twodiodes (D1, D2), of which at least a first diode (D1) connects theneutral conductor terminal (N) to a first of the smoothing capacitors(C1) and of which at least a second diode (D2) connects the neutralconductor terminal (N) to a second of the smoothing capacitors (C2).

In some embodiments, there is a control apparatus (C) that is connectedin a controlling manner to the configuration device (KV), wherein theconfiguration device (KV) is fitted with switches (S1, S2) and thecontrol apparatus (C) is designed, (i) in a parallel configurationstate, to close only the switch or switches (S1, S2) of theconfiguration device (KV) via which the smoothing capacitors (C1, C2)are each connected between two different potentials (P+, P−) of therectifier (GR), and (ii) in a series configuration state, to provide theswitch or switches (S1, S2) of the configuration device (KV) that areclosed in the parallel configuration state in the open state.

In some embodiments, the control apparatus (C) is designed to ascertaina single-phase as well as a polyphase occupancy state of the alternatingcurrent terminal (WA), to ascertain a single-phase and a polyphase usagestate of the rectifier (GR) or to acquire a signal that indicates asingle-phase or a polyphase desired state of the charging circuit,wherein the control apparatus (C) is designed to connect the smoothingcapacitors (C1, C2) to one another in a parallel configuration in one ofthe single-phase states and to connect them to one another in a seriesconfiguration in one of the polyphase states.

In some embodiments, the charging circuit comprises a plurality ofdirect voltage converters (GW1, GW2) each comprising a clocked switchingunit (SE1, SE2) and an intermediate circuit capacitor, wherein theintermediate circuit capacitor of a first of the direct voltageconverters (GW1) is formed by a first of the smoothing capacitors (C1)and the intermediate circuit capacitor of a second of the direct voltageconverters (GW2) is formed by a second of the smoothing capacitors (C2).

In some embodiments, the direct voltage converters (GW1, GW2) compriseterminals that are connected to a direct current terminal (GA)configured for connection of the energy store (ES), wherein theterminals of the direct voltage converters (GW1, GW2) are connected toone another in parallel.

In some embodiments, the rectifier (GR) is a controllable rectifier thatcomprises a controllable rectifier unit (GE) that is connected directlyto the alternating current terminal (WA), or the rectifier (GR) is apower factor correction filter that comprises a controllable rectifierunit (GE) that is connected to the alternating current terminal (WA) viainductors (I1-I3).

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE schematically shows an embodiment of a charging circuit thatis connected to a (vehicle-side) energy store incorporating teachings ofthe present disclosure.

DETAILED DESCRIPTION

In some embodiments of the teachings herein, a charging circuitcomprises two smoothing capacitors that can be connected to each otherin either a parallel or a series connection by means of a configurationdevice. A rectifier is connected to the alternating current terminal andso connects the alternating current terminal to the smoothing capacitors(with rectification). The alternating current terminal, and thereby alsothe rectifier, can be operated with different numbers of (various)phases, for example single-phase or three-phase. Different interlinkingfactors (which depend, as is known, directly on the number of phases,i.e. the number of currents, offset in phase to one another, that areused) thus result. As a consequence, due to the different interlinkingfactors, different voltage levels also result at the smoothingcapacitors when the rectifier, or the alternating current terminal, isoperated with different numbers of phases.

It is possible due to the option between parallel or seriesconfiguration of the smoothing capacitors, to configure the smoothingcapacitors economically (namely with a relatively low rated voltage),and nevertheless adjust and thereby optimize them depending on thevoltage to be smoothed or the operation of the rectifier. In the case ofsingle-phase voltage, which means with single-phase operation(corresponding to a low rectified voltage), a parallel configurationprovided to achieve a high capacitance, whereas in the case of polyphaseoperation (of the alternating current terminal or of the rectifier) andthereby a (rectified) voltage that is greater in comparison tosingle-phase operation, the serial configuration is used, so that eachcapacitor is only subjected to a part of the total voltage forsmoothing.

In some embodiments, there is a diode circuit connects the neutralconductor of the alternating current terminal appropriately to eachconfiguration. The neutral conductor terminal of the alternating currentterminal is connected to the configuration device through this. Theconfiguration device itself connects the rectifier to the smoothingcapacitors and is thus connected to the smoothing capacitors. Inpolyphase operation, the diode circuit enables asymmetric components ofthe phases of the alternating current terminal to be diverted, and thusserves for filtering. In polyphase operation, or in the serialconfiguration, the diode circuit thus serves to divert unwantedcomponents.

In asymmetric operation, which means, for example, in single-phaseoperation, the diode circuit serves to connect the neutral conductor asa diverter or as a return conductor. While one, a plurality, or all ofthe phase terminals of the alternating current terminal are subjected toone phase, or with the same phase, of the alternating current system,the neutral conductor forms the return conductor, as in usual,single-phase consumers of a 230 V alternating current grid. The diodesof the diode circuit thereby permit a connection to the (parallel)connected smoothing capacitors, in order to complete the returnconduction path (or forward conduction path) to these. The diode circuitcomprises at least one diode that is provided between the neutralconductor terminal and the configuration device. The diode circuit inparticular comprises for this purpose at least one diode connected inseries (wherein the series circuit relates to the interconnectionrelative to the neutral conductor terminal). The diode circuit cancomprise a plurality of diodes that are connected in series startingfrom the neutral conductor terminal to the configuration device. In someembodiments, at least two diodes are connected (in series), relative tothe neutral conductor terminal, in opposing directions between theneutral conductor terminal and the configuration device in this case.

The connection of the neutral conductor terminal via the diode circuitreferred to above enables the division of the smoothing capacitors, inparticular so that even at high voltages it is possible to work withcapacitors whose maximum voltage is lower than the maximum rectifiedvoltage. Through division into a series circuit, the individualsmoothing capacitors are only subject to a portion of the rectifiedvoltage. The smoothing capacitors can thereby be dimensioned for a lowerrated voltage or maximum voltage, whereby costs can be saved. The diodecircuit enables the neutral conductor terminal to be connected withoutswitches. In the case of polyphase use of the alternating currentterminal or of the rectifier, the connection serves for the diversion ofasymmetric components, whereas, in a single-phase operation (of thealternating current terminal or of the rectifier), the diode circuitserves to provide a connection between the configuration device (andthereby, finally, an energy storage terminal) and the single-phasepotential.

As another example, some embodiments include a charging circuit for avehicle-side electrical energy store, wherein the charging circuitcomprises an alternating current terminal, at least two smoothingcapacitors, a configuration device and a rectifier. The alternatingcurrent terminal is connected to the configuration device via therectifier. The configuration device connects the rectifier to thesmoothing capacitors. The configuration device is, in other words,provided between the rectifier and the smoothing capacitors. Therectifier is thus connected to the smoothing capacitors via theconfiguration device. The configuration device is configured to connectthe smoothing capacitors to one another optionally in a parallel orseries configuration. The smoothing capacitors are thus connected to theconfiguration device in such a way that in a first switch state thesmoothing capacitors are connected in parallel with one another, and ina second state (corresponding to the series configuration) they areconnected to one another in series.

The alternating current terminal comprises a neutral conductor terminal.This is connected via a diode circuit to the configuration device. Theneutral conductor terminal is thus connected to the smoothing capacitorsvia the diode circuit. The configuration device is provided between theneutral conductor terminal and the smoothing capacitors.

In some embodiments, the diode circuit comprises a plurality of diodes.These are connected (possibly with switches to one another) to differentconnection points of the configuration device. One, a plurality, or allof the diodes of the diode circuit is or are connected to the neutralconductor terminal. This at least one diode is connected in seriesbetween the neutral conductor terminal and the configuration device, inparticular to connecting points within the configuration device. Thediodes of the diode circuit may also be referred to as neutral conductordiodes, since the neutral conductor is connected thereto or since thesediodes (in particular their connecting point) are connected to theneutral conductor terminal. The diode circuit may be provided in theform of a half-bridge. The neutral conductor terminal (that is to saythe neutral conductor) is connected or able to be connected at theconnecting point within the half-bridge.

In some embodiments, the diode circuit is a rectifier circuit. The diodecircuit can here comprise a diode bridge circuit, perhaps in the form ofa half-bridge, that can comprise an intermediate point at which theneutral conductor is connected. The rectifier circuit that is formed bythe diode circuit can comprise an alternating current side, perhaps inthe form of the connecting point. This alternating current side isconnected to the neutral conductor terminal. The rectifier circuitformed by the diode circuit can comprise a direct current side that isconnected to the configuration device (and thereby also to thecapacitors). The rectifier circuit is, in particular, a full-waverectifier circuit.

In some embodiments, the diode circuit can comprise at least two diodes.The different diodes may be connected to different smoothing capacitors.With reference to the neutral conductor terminal, the different diodesare connected in opposing directions (with reference to the forwardconduction direction or the reverse bias direction). A first diode ofthe two diodes can connect the neutral conductor terminal to a first ofthe smoothing capacitors. A second diode of the at least two diodes canconnect the neutral conductor terminal to a second of the smoothingcapacitors. As seen from the neutral conductor terminal, the forwardconduction directions of the two diodes are opposed to one another. Bothhalf-waves are thereby conducted by the diodes, wherein the differentdiodes conduct half-waves of different polarities (to the capacitors).The connection between the smoothing capacitors and the diodes yields aseries interconnection of the respective diode to the smoothingcapacitor. This allows a particularly economical representation of thediode circuit that is equally well designed for single-phase and forpolyphase charging.

In some embodiments, the configuration device comprises at least onefirst switch. When closed, this connects the smoothing capacitors to oneanother in parallel. The at least one first switch therefore establishesthe parallel connection between the smoothing capacitors. Theconfiguration device can comprise one or more diodes (or generally adiode circuit) that (when closed) connect the smoothing capacitors toone another in series. In the forward conduction direction, the diodethus connects the smoothing capacitors to one another in series.

In some embodiments, the configuration device comprises two firstswitches and a first diode. The two first switches can also be referredto as parallel switching elements, since, when closed, they connect thesmoothing capacitors to one another in a parallel circuit. Theconfiguration device can, furthermore, comprise a diode that can also bereferred to as the serial switching element, since, in the forwardconduction direction, it connects the smoothing capacitors to oneanother in series. The two first switches and the diode are connected toone another in series, in particular in a series circuit. This seriescircuit is connected to different potentials of the rectifier. In otherwords, the two first switches and the diode are connected to one anotherin a series circuit that is connected in parallel with the rectifier.The switches and the diode are connected to one another in a seriescircuit that is connected to different potentials of the rectifier. Thediode is connected in series with the first switches. The diode isprovided between the first switches. The diode connects the switches toone another (in series). The diode is connected in the reverse biasdirection with respect to the potentials of the direct voltage side ofthe rectifier. In embodiments that do not have any further switches, thetwo first switches of the configuration device may also be referred toas two switches or two configuration switches. The diode of theconfiguration device may be referred to as configuration diode, since itis part of the configuration device.

In some embodiments, the first switches are connected to one another, inthe context of the series circuit, via the diode. The first switchesthus comprise terminals that are connected directly to the differentpotentials of the rectifier. In this context, potentials of therectifier refer to direct voltage potentials, which means on the directvoltage side of the rectifier. The diode connects the two first switchesto one another. Since the diode is connected between the first switches,and the first switches are connected directly to the two potentials, thediode is not connected to the potentials directly, but via the firstswitches. The potentials of the rectifier correspond to the rectifiedvoltage that results from the voltage at the alternating currentterminal and the relevant interlinking factor. The different potentialsare, in particular, a positive and a negative potential, but can howeveralso be a ground potential and a positive potential.

In some embodiments, the charging circuit comprises a control apparatusthat is connected in a controlling manner to the configuration device.The configuration device is fitted with switches. The control apparatusis connected in a controlling manner to the switches. In a parallelconfiguration state (for the charging control device) the controlapparatus is designed to close only the switch or switches of theconfiguration device via which the smoothing capacitors are eachconnected between two different potentials of the rectifier. In otherwords, the control apparatus is designed to close only the switch orswitches of the configuration device which, when closed, connects thesmoothing capacitors to one another in parallel (and thereby alsoconnects to the two different potentials). In the parallel configurationstate, each of the smoothing capacitors is separately connected betweenthe two different potentials, and thus receives the full potentialdifference or voltage between the two different potentials.

In some embodiments, the controller ascertains a single-phase as well asa polyphase occupancy state of the alternating voltage terminal. In someembodiments, the controller ascertains a single-phase and a polyphaseusage state of the rectifier. In some embodiments, the control apparatusacquires a signal that indicates a single-phase or a polyphase desiredstate of the charging circuit. The control apparatus is in other wordsdesigned to distinguish between a single-phase and a polyphase state (ofthe alternating current terminal or of the rectifier). The controllercan furthermore be designed to connect the smoothing capacitors to oneanother in a parallel configuration in one of the single-phase states.The control apparatus is furthermore designed to connect the smoothingcapacitors to one another in a series configuration in one of thepolyphase states.

In some embodiments, the control apparatus, in the case of a rectifiedvoltage that is present at the direct current side of the rectifier andthat lies above a predefined threshold value, connects the smoothingcapacitors to one another in series (by means of the configurationdevice), and in the case of a voltage that does not lie above thethreshold value, connects the smoothing capacitors to one another inparallel (again by means of the configuration device). It is therebypossible, that even increased voltages that do not result from anincreased interlinking factor (i.e. an interlinking factor>1), for thesmoothing capacitors to be connected in series (in order thus to obtainonly a part of the rectified voltage per capacitor). The controlapparatus can therefore comprise a comparator that compares therectified voltage of the rectifier to the threshold value. In someembodiments, the threshold value lies below a maximum voltage of thecapacitors by a predefined margin determined by the design of thecapacitor.

In some embodiments, the charging circuit comprises a plurality ofdirect voltage converters. These each comprise a clocked switching unitand an intermediate circuit capacitor. The intermediate circuitcapacitor of a first of the direct voltage converters is formed by afirst of the smoothing capacitors. The intermediate circuit capacitor ofa second of the direct voltage converters is formed as a second of thesmoothing capacitors. The smoothing capacitors are thereby used asintermediate circuit capacitors of different direct voltage converters.In some embodiments, the smoothed switching unit comprises at least onecontrollable switch, in particular two controllable switches, whereinthese switches serve for the alternating connection of an element. Thedirect voltage converter can, for example, comprise an inductor (or acapacitor) as a temporary storage element. In some embodiments, eachdirect voltage converter comprises a converter inductor that isconnected upstream or downstream of the clocked switching unit. Thedirect voltage converters can be designed as step-up, step-down orsynchronous converters. The direct voltage converters are preferablyconstructed in the same manner.

In some embodiments, the direct voltage converters comprise terminalsthat are connected to a direct current terminal. The direct currentterminal is configured for connection of the energy store (to thecharging circuit). The terminals of the direct voltage converters arehere connected to one another in parallel. The direct voltage convertersthus operate in parallel when charging, and the currents that aredelivered are added together at the direct current terminal. A positiveand a negative terminal are, for example, provided as terminals, whereinboth of the direct voltage converters, or their positive potentials, areconnected at the positive terminal. The same also applies to thenegative terminal or for a ground terminal.

In some embodiments, the rectifier is controllable. The controllablerectifier can be connected directly to the alternating current terminal.The rectifier unit here comprises transistors, but not, however, anydedicated energy stores such as coils.

In some embodiments, the rectifier can be a power factor correctionfilter. This comprises a controllable rectifier unit that is connectedvia inductors (such as coils) to the alternating current terminal. Theinductors here form temporary energy stores in the context of the powerfactor correction filter. Each phase of the alternating current terminalis connected to the rectifier unit via its own (series-connected)inductor.

As another example, some embodiments include a vehicle electrical systemthat comprises the charging circuit and an energy store that isconnected to this via the direct current terminal of the chargingcircuit. If a direct voltage converter is not provided, then the directcurrent terminal (for connecting to the energy store) is joined directlyto the direct voltage side of the rectifier, which means with thepotentials between which the intermediate smoothing capacitors arelocated.

The FIGURE schematically shows one embodiment of a charging circuit thatis connected to a (vehicle-side) energy store incorporating teachings ofthe present disclosure. The charging circuit LS shown comprises analternating current terminal WA with three phase terminals L1 to L3, andwith a neutral conductor terminal N. These are connected to analternating current side of a rectifier GR. The rectifier GR comprises arectifier unit GE with diodes, as well as three inductors I1 to I3 (withindividual phases) connected upstream. The inductors I1 to I3 connectthe alternating current terminal WA to the rectifier unit GE, and inparticular connect the different phase terminals L1-L3 of thealternating current terminal to the rectifier unit GE. The rectifierunit GE only comprises rectifier elements in the form of diodes or, inparticular, in the form of controllable transistors. The inductors I1 toI3 with individual phases connected upstream, together with therectifier unit, form a power factor correction filter, which means arectifier GR which, in addition to the rectifying function, alsorealizes functions such as harmonic damping and/or power factorcorrection and/or stepping up.

The rectifier GR comprises a direct current side GS that is opposite tothe alternating current side. The rectifier GR thus connects thealternating current terminal WA to two individual ends of a pair ofsmoothing capacitors C1 and C2. A diode circuit DE is provided,comprising a first diode D1 and a second diode D2. These are connectedto one another in series via a connecting point, wherein the neutralconductor terminal N is connected at the connecting point. Looking outfrom this connecting point, the diodes D1 and D2 are connected (inopposing forward conduction directions) to a configuration device KV.

The configuration device KV comprises a series circuit of two switchesS1 and S2, as well as a diode DS. These are connected to one another inseries. The resulting series circuit is connected to the direct currentside of the rectifier GR. This series circuit of the switches S1 to S3is in particular connected with one end to the positive potential P+ andthe negative potential P−. The positive potential P+ and the negativepotential P− are the direct voltage potentials of the rectifier GR or ofthe direct current side GS of the rectifier GR. The series circuit ofthe switches S1 to S3, and thereby the configuration device KV, isconnected in parallel (with the ends of the configuration device KV) tothe potentials P−, P+. The diode DS connects the switches S1 and S2 toone another. The switches S1 and S2 are each permanently connected toone of the two potentials, wherein the switch S1 is connected to thepositive potential P+ and the switch S2 is connected to the negativepotential P−. The series circuit of the diodes D1 and D2 is connected inparallel with the diode DS, which is connected in series between theswitches S1 and S2.

The diode circuit DE is in other words connected in parallel with thediode DS. The diode circuit DE forms a diode bridge for full-waverectification, in particular for single-phase operation. The connectingpoint of the diodes of the diode circuit DE is connected to the neutralconductor N.

The connecting point between the switch S1 and the diode DS is connectedto a first smoothing capacitor C1. The connecting point between thediode DS and the switch S2 is connected to the second smoothingcapacitor C2. The smoothing capacitors C1 and C2 are thus only connectedin series with one another when the diode DS is not conducting. If theswitches S1 and S2 are closed, then the capacitors C1 and C2 areconnected to one another in parallel.

If only one phase is thus connected, an interlinking factor of 1results, and the capacitors C1 and C2 can be connected in parallel withone another to increase the capacitance. If the alternating currentterminal WA is used with three phases (wherein the phase terminals L1 toL3 are connected to different phases of a three-phase current system),an interlinking factor>1 results, and the capacitors C1 and C2 areconnected in series by the configuration device KV. As a result (due tothe voltage division of the capacitors) only half of the smoothedvoltage is developed across each of the capacitors C1 and C2. Each ofthe capacitors C1 and C2 can thereby be dimensioned with a lower ratedvoltage than the maximum voltage in three-phase operation. The smoothingcapacitors preferably have the same (nominal) capacitance and/or thesame rated voltage.

In single-phase operation, the neutral conductor N can be connected to acorresponding terminal of the three-phase system, while the phaseterminals L1 to L3, or only the phase terminal L2 (or also only thephase terminal L1 and L2) are connected to one and the same phase of theconnectable network. An interlinking factor of 1 results in this case.When more than one phase terminal L1 to L3 is connected to the samephase of a connectable alternating current network, the relevantterminals L1, L2, L3 are accordingly connected to one another. Since nophase currents that are offset in phase with respect to one another areused, or no phase terminals with phase offset are connected, this isalso referred to as single-phase operation. In single-phase operation,the terminals L1, L2 and L3 are preferably connected to the same phase(i.e. connected to one another), so that all the phases of the rectifierGR can contribute to the flow of current.

In some embodiments, the smoothing capacitors C1 and C2 or the directvoltage side of the rectifier GR are/is connected directly to the energystore ES, the direct current terminal GA of the charging circuit LS. Theenergy store ES here is not necessarily part of the charging circuit,but can be a further component of the vehicle electrical network inwhich the charging circuit is provided.

In the example illustrated, a direct voltage converter unit WE thatcomprises two direct voltage converters GW1, GW2, is provided. Each ofthe voltage converters GW1, GW2 comprises a switching unit SE1, SE2.Clocked switching elements of the direct voltage converter are providedin these as well as a temporary energy store (here illustratedsymbolically) such as a coil. The intermediate circuit capacitorsbelonging to the direct voltage converter are realized by the capacitorsC1 and C2. The first direct voltage converter GW is thus formed from thecapacitor C1 as an intermediate circuit capacitor and the switching unitSE1. The direct voltage converter GW2 is correspondingly formed from theswitching unit SE2 and the capacitor C2.

A control apparatus C is connected in a controlling manner to theswitches S1 and S2. The control apparatus C can furthermore comprise aninput at which the control apparatus can acquire signals relating to thenumber of active (different) phases of the rectifier GR. These can besignals that represent the occupancy status of the alternating currentterminal, that represent the number of active and phase-offset phases ofthe rectifiers GR, or that represent a command to carry out asingle-phase or polyphase operation, wherein the last-mentioned signalstates the number of the (different) phases. In a further form ofembodiment, the control apparatus C is designed to acquire the voltageat the direct current side of the rectifier and from that to deducewhether the voltage is greater than a threshold value, in order in thiscase to provide the configuration device KV for series operation (of thecapacitors C1 and C2). If the voltage is lower than the threshold value,the configuration device is set to parallel interconnection of thesecapacitors in order to increase the total capacitance of the capacitorsC1 and C2.

The direct voltage converter unit WE is only shown schematically. Thedirect voltage converters GW1, GW2 or switching units SE1, SE2, that arepresent there are connected in parallel with one another at the output,which means at the side of the direct current terminal GA. A seriesconnection of the converter is, however, also conceivable. Galvanicallyconductive or galvanically isolating or insulating converters can beprovided as the converters GW1, GW2. This depends on the interconnectionat the side of the direct current terminal GA.

It should finally be noted that the FIGURE can be viewed as the vehicleelectrical network that comprises the charging circuit LS and the energystore ES connected thereto. The energy store ES can be an accumulator,in particular a lithium-based accumulator. The energy store ES may be atraction accumulator. The charging circuit may be designed for a powerof at least 1 kW, 5 kW, 10 kW or 50 kW. This relates to the power whenconnected to a three-phase system.

What is claimed is:
 1. A charging circuit for a vehicle-side electricalenergy store, the charging circuit comprising: an alternating currentterminal; two smoothing capacitors; a configuration device; and arectifier connecting the alternating current terminal to theconfiguration device; wherein the configuration device connects therectifier to the smoothing capacitors, and the configuration device isprogrammed to connect the smoothing capacitors to one another in a firstparallel connection and a second series connection; wherein thealternating current terminal comprises a neutral conductor terminalconnected to the configuration device via a diode circuit; wherein theconfiguration device comprises a first switch connecting the smoothingcapacitors to one another in parallel when closed; and wherein theconfiguration device comprises a diode connecting the smoothingcapacitors to one another in series when closed.
 2. The charging circuitas claimed in claim 1, wherein: the configuration device comprises twofirst switches and a diode are connected to one another in a seriescircuit connected to at least two different potentials of the rectifier;and the first switches are connected to one another within the seriescircuit via the diode.
 3. The charging circuit as claimed in claim 1,wherein the diode circuit comprises a rectifier circuit with analternating current side connected to the neutral conductor terminal anda direct current side connected to the configuration device.
 4. Thecharging circuit as claimed in claim 1, wherein: the diode circuitcomprises two diodes; a first diode of the two diodes connects theneutral conductor terminal to a first of the two smoothing capacitors;and a second diode of the two diodes connects the neutral conductorterminal to a second of the two smoothing capacitors.
 5. The chargingcircuit as claimed in claim 1, further comprising a control apparatusconnected in to the configuration device; wherein the configurationdevice includes two switches and is programmed, (i) in a parallelconfiguration state, to close only the switch or switches via which thetwo smoothing capacitors are each connected between two differentpotentials (P+, P−) of the rectifier; and (ii) in a series configurationstate, to open the switch or switches that are closed in the parallelconfiguration state.
 6. The charging circuit as claimed in claim 5,wherein the control apparatus is programmed to: ascertain a single-phaseversus a polyphase occupancy state of the alternating current terminal;ascertain a single-phase versus a polyphase usage state of the rectifieror to acquire a signal that indicates a single-phase or a polyphasedesired state of the charging circuit; connect the two smoothingcapacitors to one another in a parallel configuration in one of thesingle-phase states and to connect them to one another in a seriesconfiguration in one of the polyphase states.
 7. The charging circuit asclaimed in claim 1, wherein: the charging circuit comprises a pluralityof direct voltage converters each comprising a clocked switching unitand an intermediate circuit capacitor; the intermediate circuitcapacitor of a first of the direct voltage converters includes a firstof the two smoothing capacitors; and the intermediate circuit capacitorof a second of the direct voltage converters includes a second of thetwo smoothing capacitors.
 8. The charging circuit as claimed in claim 7,wherein: the direct voltage converters each comprise terminals connectedto a direct current terminal configured for connection of the energystore; and the terminals of each of the direct voltage converters areconnected to one another in parallel.
 9. The charging circuit as claimedin claim 1, wherein: the rectifier comprises a controllable rectifierunit connected directly to the alternating current terminal; or therectifier comprises a power factor correction filter with a controllablerectifier unit connected to the alternating current terminal viainductors.